Quantifying and interpreting nestedness of bryophytes in the Zhoushan Archipelago, China

The distribution data of 18 categories (including 446 species) of bryophytes in 66 islands of the Zhoushan Archipelago, China were complied. By using the matrix temperature and the NODF metrics under six null models, we evaluated their nestedness levels and explored possible mechanisms to form nested distribution with partial Spearman correlation and the random placement model. The main results were as follows: 1) all the 18 categories of bryophytes exhibited a high degree of nestedness; 2) nestedness level was higher for mosses than liverworts, higher for acrocarpous mosses than pleurocarpous mosses, and also varied among families; 3) the nested distribution of bryophytes in the archipelago was not due to passive sampling, but mainly due to nested habitats and selective-extinction; 4) spore size might be a factor linked to selective-colonization accounting for nestedness of some bryophyte categories; and 5) nestedness level was higher for families with a high proportion of generalists than those with a high proportion of specialists, the conservation of the latter should cover more islands (patches).